Method and apparatus for temperature sensing

1. A temperature sensing system for monitoring the temperature of a processor having a clock and for modulating processor operations when an overtemperature condition is detected, comprising: a temperature sensor, having means for receiving a temperature input and an output for carrying a sensor output signal, said sensor output signal having a frequency related to said temperature input; and modulation means, external to said processor and operatively coupled to receive said sensor output signal and having a modulation output operatively coupled to said processor, for monitoring said frequency, for detecting, based on said frequency, whether an overtemperature condition has occurred, and for periodically asserting and deasserting a modulation signal, independent of said clock, on said modulation output for controlling said processor clock, thereby controlling the temperature of said processor.

2. The temperature sensing system of claim 1, wherein said temperature sensor includes: a temperature sensitive current source, having an output for carrying a current; current converting means for generating a voltage from the current; and a voltage controlled oscillator operatively coupled to receive said voltage and having a VCO output for carrying said sensor output signal.

3. The temperature sensing system of claim 1, wherein said modulation means includes: a counter, operatively coupled to receive said sensor output signal, said counter for producing a count value; storage means for storing a frequency threshold value; and comparison means, for comparing said counter value to said frequency threshold value.

4. The temperature sensing system of claim 3, wherein said storage means is a programmable register.

5. The temperature sensing system of claim 1, wherein said modulation signal is a STPCLK# signal and wherein said modulation means is for asserting said STPCLK# signal on said modulation output when said frequency reaches a frequency threshold value, indicating an overtemperature condition.

6. The temperature sensing system of claim 5, wherein said modulation means is further for operating in a fail safe mode when a system failure condition is present.

7. The temperature sensing system of claim 6, wherein said system failure condition is a zero frequency and wherein said fail safe mode includes asserting said STPCLK# signal.

8. An apparatus for monitoring the temperature of a processor and for modulating processor operations when an overtemperature condition is detected, comprising: a temperature-to-frequency converter, having an output; and a thermal management unit in communication with said temperature-to-frequency converter and said processor, said thermal management unit external to said processor and including: a frequency monitor in communication with said temperature-to-frequency converter output, said frequency monitor having an output and structured to produce a frequency value after a predetermined time period; a comparator, having a first input in communication with said frequency monitor output and a second input for carrying a threshold frequency value, said comparator having a modulation output in communication with said processor, said comparator structured to periodically assert and deassert a signal on said modulation output indicative of whether said frequency value is at least said threshold frequency value.

9. The apparatus of claim 8, wherein said temperature-to-frequency converter includes: a voltage controlled oscillator; and a temperature-to-voltage converter.

10. The apparatus of claim 8, wherein said thermal management unit further includes: a register coupled to said second input of said comparator, said register storing said threshold frequency value.

11. The apparatus of claim 10, wherein said frequency monitor includes: a counter; and a timer coupled to said counter.

12. The apparatus of claim 8, wherein said signal carried on said modulation output interacts with a STPCLK# feature on said processor.

13. A method for monitoring and controlling temperature of a processor having a clock and for modulating processor operations, comprising the steps of: sensing a temperature; producing a signal having a frequency related to temperature; comparing said frequency to a threshold frequency value; and if said frequency is at least said threshold frequency value, periodically asserting and deasserting a STPCLK# signal to a STPCLK# input of said processor thereby controlling the temperature of said processor.

14. A method for monitoring temperature of a processor having a clock and modulating processor operations, comprising the steps of: sensing a temperature; producing a signal having a frequency related to temperature; comparing said frequency to a threshold frequency value; and periodically asserting and deasserting, if said frequency is between a first frequency value and a second frequency value higher in frequency than said first frequency value, a STPCLK# signal to a STPCLK# input of said processor, at a first modulation level, and periodically asserting and deasserting, if said frequency is above said second frequency value, said STPCLK# signal to a STPCLK# input of said processor, at a second modulation level higher in level of modulation than said first modulation level.